It has been recognized that, for space and storage considerations, it is more economical to stack containers one on top of the other. One primary disadvantage of stacking larger containers, however, is the weight that must be borne by the containers at the bottom of the stack. Even in situations where the containers can support the weight, the container lids may not be strong enough. This problem is particularly acute when plastic containers having plastic tops or using plastic lids are employed.
The present invention overcomes this particular disadvantage by providing a container closure having a valve stem associated with an inflatable bladder positioned beneath the container top. Once inflated, this bladder presses against the material within the container and the underside of the top of the container and provides structural support for the top of the container.
The closure of the present invention includes a threaded plug adapted to be received within a corresponding opening of the container lid. The plug has a central aperture through which a valve stem extends to facilitate access to the valve stem exteriorly of the closure. Seated within the aperture of the plug is a valve adapter which forms a housing for the stem. The valve adapter is snap-fit into the aperture and the valve stem is threadably received within the adapter. A removable cap fits over the stem and adapter to protect against contaminants and damage to the valve.
The valve stem forms a part of an inflatable bladder adapted to support the container lid. However, the closure plug, including the valve and bladder, may be removed to allow access to the materials within the container. Following filling of the container, the container lid, with the closure installed and the bladder on the underside of the lid, is mounted to the container. The valve stem is used to inflate the bladder positioned between the container contents and container lid in order to provide support for the lid. When it becomes necessary to access the container contents, the closure is removed to expose the opening and the container contents.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.